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RA599  B28  The  sanitary-chemica 


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Columbia  <intoet*itp 
intljeCttpoflftewgork 

College  of  $f)2»«iriana  anb  ^>urgeon« 
Htbrarp 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

Open  Knowledge  Commons 


http://www.archive.org/details/sanitarychemicalOObart 


The  Sanitary  -  Chemical   and 

Bacteriological  Examination 

of  Natural  Ice 


AN  ADDRESS 
By  EDWARD  BARTOW 

Directoi  Illinois  State  Water  Survey 


The  Natural  Ice  Association  of  America 

1 1 6  Nassau  Street 

NEW  YORK,  N.  Y. 


* 

-  THE  SANITARY— CHEMICAL  AND  BACTERIOLOGICAL  EX 

:•-  AMINATION  OF  NATURAL  ICE. 

J 

By  Edward  Bartow,  Director  Illinois  State  Water  Survey. 

DURING  the  past  two  or  three  years  the  Illinois  State  Water 
Survey  has  been  called  upon  to  make  some  sanitary  examina- 
tions of  natural  ice.  In  a  few  cases  we  have  received,  with  the 
ice,  samples  of  the  water  from  which  the  ice  was  harvested.  The  com- 
parative analyses  are  especially  interesting.  I  wish  every  much  that 
there  were  more  analyses  to  place  before  you,  but  the  data  obtained 
are  enough  to  warrant  some  interesting  conclusions. 

The  analyses  made  have  been  arranged  in  two  tables.  The  first 
table  shows  the  data  obtained  by  the  analyses  of  the  specimens  of  ice. 
The  second  table  shows  a  comparison  of  the  analyses  of  some  specimens 
of  ice  with  the  analyses  of  the  water  from  which  the  ice  was  harvested. 

The  determinations  made  are  the  ordinary  determinations  of  chem- 
ical and  bacteriological  analysis,  including  turbidity,  color,  odor,  residue, 
chlorine,  oxygen  consumed,  nitrogen  as  free  ammonia,  albuminoid 
ammonia,  nitrites  and  nitrates,  alkalinity,  the  number  of  bacteria  and 
gas  formers.  Some  of  these  tests  are  of  little  significance  in  ice  analysis 
but  others  have  a  decided  value. 

Turbidity  refers  to  the  insoluble  matter  in  suspension.  It  may  be 
dangerous  or  harmless.  Even  if  harmless  it  renders  a  water  or  an  ice 
less  attractive  than  a  clear  water.  In  only  one  ice  did  the  turbidity 
exceed  five  parts  per  million  and  in  the  one  which  is  reported  as  greater 
there  is  so  small  a  residue  that  one  must  conclude  that  there  may  have 
been  an  error  in  the  work. 

Color  refers  to  colored  substances  in  solution.  It  is  due  usually 
to  an  extract  of  vegetable  matter.  Color  is  usually  harmless,  but  a 
colored  water  or  ice  arouses  suspicion  and  people  will  not  use  it.  The 
color  of  all  of  the  samples  was  very  low;  and  in  no  case  would  it  be 
detected  in  an  ordinary  drinking  glass. 

Odor  is  a  descriptive  term  and  is  reported  as  aromatic,  earthy, 
vegetable,  etc.  Only  one  of  the  samples  was  reported  as  having  a  notice- 
able aromatic  odor.  Only  one  of  the  samples  was  reported  as  having 
a  noticeable  odor. 

"Residue"  comprises  the  solid  matter  left  on  evaporating  the 
water.  It  includes  both  organic  and  inorganic  constituents.  Unless 
the  quantity  is  excessive,  it  does  not  injure  the  water  for  domestic  use. 
Five  hundred  parts  per  million  is  a  usual  allowance  in  a  drinking  water. 
Ice  should  have  very  little  residue.  The  highest  residue  found  in  the 
ice  examined  was  3-4  parts  per  million,  but  in  most  cases  it  was  less 
than  10,  which  is  the  equivalent  of  distilled  water. 

"Chlorine"  refers  to  the  quantity  of  chlorine  in  combination  with 


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metals;  for  example,  sodium  chloride  (common  salt).  Chlorine  is  a 
constant  and  considerable  constituent  of  sewage.  Unless  present  be- 
cause of  the  presence  of  salt  wells,  or  the  nearness  to  the  sea,  etc.,  its 
presence  in  a  water  is  a  cause  for  suspicion.  The  chlorine  in  the  ice 
examined  never  exceeded  3  parts  per  million.  It  usually  could  be 
determined  with  difficulty,  and  could  well  be  reported  as  "trace." 

The  "alkalinity"  refers  to  the  soluble  carbonates  or  hydrates,  and 
helps  to  determine  the  value  of  a  water  for  household  uses.  There 
should  be  a  very  low  alkalinity  in  an  ice,  as  was  found  to  be  the  case 
In  the  specimens  examined. 

While  they  indicate  very  well  the  purity  of  the  ice  from  a  physical 
and  chemical  standpoint,  the  tests  for  turbidity,  color,  odor,  residue, 
chlorine  and  alkalinity  are  of  no  significance  with  respect  to  the  hygienic 
condition  of  the  water. 

In  Table  2  are  shown  analyses  of  ice  and  the  water  from  which 
the  ice  was  taken.  A  consideration  of  the  degree  of  purification  effected 
by  freezing  is  quite  interesting,  from  both  a  chemical  and  bacteriological 
standpoint. 

The  turbidity,  although  not  high  in  the  original  water,  is  practically 
eliminated. 

The  high  color  in  most  of  the  samples  was  also  eliminated,  in  two 
of  the  cases  being  reduced  from  50  to  0. 

The  residue  was  reduced  from  183  to  11,  194  to  10  and  197  to  10 
respectively. 

The  chlorine  was  reduced  from  2.4  to  0,  2.3  to  1  and  3  to  .2;  the 
alkalinity  from  134  to  1,  144  to  3,  180  to  1. 

The  oxygen  consumed  was  reduced,  and,  in  most  cases,  free  and 
albuminoid  ammonia,  nitrites  and  nitrates  were  greatly  reduced. 

Where  comparisons  of  the  number  of  bacteria  were  made,  the 
purification  was  very  striking.  In  one  case,  with  12,000  bacteria  in  the 
raw  water,  there  were  but  125  in  the  ice;  520  were  reduced  to  3,  675 
to  6,  1,400  to  16,  and  4,060  to  22,  in  every  case  practically  99%  reduc- 
tion.    Gas-forming  bacteria  were  also  greatly  reduced. 

In  the  purification  of  water  by  freezing  both  suspended  matter  and 
soluble  substances  are  removed.  The  removal  of  the  suspended  matter 
is  explained  by  the  fact  that  water  in  freezing  solidifies  on  top.  The 
formation  of  the  coating  of  ice  protects  the  water  from  disturbance 
and  enables  the  particles  heavier  than  water  to  sink  to  the  bottom. 
Also  in  the  normal  formation  of  the  crystalline  ice  there  is  no  room  for 
solids  between  the  crystals.  This  accounts  for  the  decrease  in  the 
turbidity  and  bacteria. 

For  the  removal  of  soluble  substances  we  must  seek  another  ex- 
planation. Let  us  compare  the  solubility  of  the  ice  with  the  solubility 
of  soluble  substances.     Ice  is  soluble  in  water  at  4  degrees  Centigrade 


(39.2  degrees  Fahrenheit)  when  the  water  is  at  its  maximum  density, 
but  insoluble  in  water  at  0  degrees  Centigrade  (32  degrees  Fahrenheit). 
The  substances  occurring  in  river  and  pond  waters  are,  as  a  rule,  soluble 
to  a  much  greater  extent  than  is  their  concentration  in  the  rivers  and 
ponds.  For  example,  the  least  soluble  of  the  common  substances 
occurring  in  pond  waters  is  calcium  bicarbonate.  This  at  0  degrees 
Centigrade  has  a  solubility  of  700  parts  per  million.  In  most  of  the 
streams  of  the  United  States  we  find  less  than  200  parts  per' million 
of  residue  and  hence  much  less  than  that  amount  of  any  one  compound. 
Before  very  much  calcium  carbonate  would  be  taken  from  the  water 
by  the  ice,  there  must  be  a  concentration  several  times  the  ordinary 
concentration  in  the  water.  The  same  is  true  of  other  salts.  Mag- 
nesium carbonate  is  soluble  1,300  parts  per  million.  Calcium  sulphate 
is  soluble  to  the  extent  of  2,050  parts  per  million.  Magnesium  sulphate 
is  soluble  to  the  extent  of  257,000  parts  per  million.  Of  the  salts  of 
sodium,  sodium  chloride  (common  salt)  is  soluble  to  the  extent  of 
55,000  parts  per  million.  Other  salts,  sodium  carbonate  is  soluble  to 
70,000  parts  per  million,  and  sodium  bicarbonate  to  79,000  parts  per 
million.  None  of  these  exist  in  the  rivers  and  streams  of  the  United 
States  to  an  extent  greater  than  200  parts  per  million.  Only  in  sea 
water  do  we  find  these  salts  present  in  sufficient  quantities,  so  that  on 
cooling  to  zero  degrees  are  they  taken  out  with  the  ice.  Sea  water  con- 
tains 3%  per  cent  of  salts.  The  water  obtained  from  the  melted  ice 
from  sea  water  is  said  to  be  fresh.  This,  however,  has  a  bitter  taste, 
since  but  four-fifths  of  the  salts  present  are  removed. 

Nature  certainly  does  its  share  toward  furnishing  a  pure  natural 
ice.  If  reasonable  precautions  are  taken  so  that  no  ice  is  obtained 
from  grossly  polluted  ponds  or  rivers  and  the  surface  of  the  ice  is  pro- 
tected, there  need  be  no  difficulty  in  placing  a  pure  ice  on  the  market. 
This,  I  believe,  is  the  aim  of  this  Association,  and  it  can  not  be  too 
highly  commended. 


COLUMBIA   UNIVERSITY 

This  bqgk  is  due  on  the  date  indicated  below,  or  at  the 
expiration  of  a  definite  period  after  the  date  of  borrowing, 
as  provided  by  the  rules  of  the  Library  or  by  special  ar- 
rangement with  the  Librarian  in  charge. 

DATE  BORROWED 

DATE  DUE 

DATE  BORROWED 

DATE  DUE 

C28(638)M50 

HA599 
Bart  B28 


ow 


Thai  so«u. 

RA  sj?  gag 


